The Florida Health Department and state officials have announced that they have identified four cases of Zika virus infection that were most likely transmitted locally. These cases are in Wynwood, an area just north of Miami

This is probably the first time that mosquito-borne transmission of Zika virus has happened in the continental US.

The CDC and Florida are saying “likely” and “probably” because, although they cannot yet prove these individuals were bitten by infected mosquitoes, there seems to be no other method of transmission in these cases, and the mosquito that carries the virus does live in the area.

However, this does not mean that the Zika virus will become widespread in the US.

The Zika virus is transmitted a few ways. The most common way for people to get the Zika virus is to be bitten by an infected Aedes species mosquito (Ae. aegypti and Ae. Albopictus).

This mosquito doesn’t like the climate in all parts of the US. Much of the northern area will not be at risk from this mode of transmission.

Also, this mosquito never travels more than 150 meters its entire life. That’s less than 1/10th of a mile. It usually travels far less than that distance.

The West Nile virus, on the other hand, was able to pretty much cover the US because the virus can be transmitted from an infected mosquito to a bird, which then flies off quite a distance before landing and getting bitten by a different mosquito, which then becomes infected. That mosquito, in turn, bites another bird. This cycle hopscotches its way across the US, spreading disease from bird to mosquito to bird to mosquito.

The mosquitoes also infect humans and other mammals with West Nile virus.

The mosquitoes that carry the Zika virus don’t work that way. They prefer to only bite humans.

Another reason the Zika virus will probably not explode across the US is because where the mosquito lives, people use screens across their windows and doorways, and they use air conditioning. It’s more difficult for the mosquito to get into the houses.

There are other ways for the Zika virus to be transmitted.

An infected pregnant woman can pass it to her fetus during pregnancy or around the time of birth.

An infected individual can pass the virus through sex with their partner. An infected person may or may not be symptomatic—they can still transmit the virus. It appears that four out of five infections are asymptomatic. One cannot assume that a person is virus-free just because they don’t seem to be sick.

An infected person may donate blood and the virus can then be passed through blood transfusions.

This virus is under a lot of scrutiny. New methods of transmission may be identified, but these are the primary methods at this time.

Now we have an idea of how it’s transmitted. What can we do about it?

Where pockets of infection have occurred, the state and local authorities have started aggressive mosquito control, including spraying and going door to door to alert residents to standing water. Mosquitoes love to lay eggs in standing water—making sure there is none helps to control the mosquito population.

We all need to prevent mosquito bites by using insect repellent containing DEET, wearing long sleeves and pants, and staying indoors unless covered and protected. This is particularly true for pregnant women, and for those living in areas where these mosquitoes are common.

The dengue fever virus is the most common virus that mosquitoes transmit and infects about 100 million people worldwide every year, killing about 25,000. In spite of this frequency, though, the United States, with the exception of Puerto Rico, has been mostly dengue-free for decades—until 2009.

image by infidelic

That year, a woman in New York turned up with a dengue infection, having just returned from a trip to the Florida Keys. Her case was the first of a handful that led public officials to conduct a survey of the Key West population. To their shock, they found that about 5% of residents, or about 1000 people, showed evidence of dengue exposure in 2009.

The mosquito that carries the virus occurs in warm areas of the country, including Florida and Texas, and indeed, isolated cases of dengue have cropped up a few times since the 1980s along the Texas–Mexico border. But the cases in 2009 and more in 2010 have authorities concerned that dengue now has achieved an intractable foothold on the continental United States.

Work on a vaccine against dengue is ongoing, but in the meantime, the only preventive is to avoid the bug that carries the virus: the mosquito.

Wearing repellent when in areas where they occur is one tactic. Another is removing breeding places, such as any containers with standing water. The precautions apply wherever you’re going, whether to areas where dengue is already endemic or where it is emerging. The CDC provides regular updates for travelers, including a page specific to the Florida cases.

Dengue fever can hit hard or harder, depending on the symptom severity. The “mild” version of the disease can involve a high fever, a rash, severe headache and pain behind the eyes, and nausea and vomiting. Given that these symptoms are largely nonspecific, if you see your doctor about them and have traveled in a place where dengue fever occurs, be sure to mention it. A more severe form of dengue fever is dengue hemorrhagic fever, which begins much like the “mild” form but then progresses to symptoms that can include nosebleed and signs of bleeding under the skin, known as petechiae. This form of dengue can be fatal.

The most severe manifestation of the disease, dengue shock syndrome, includes the symptoms of the milder forms along with severe abdominal pain, disorientation, heavy bleeding, and the sudden drop in blood pressure that signals deadly shock. Onset is typically four to seven days after exposure, and the mild form usually lasts only a week, while the more severe forms can involve either a progressive worsening or a sudden worsening following an apparent improvement.

Oddly enough, having dengue fever once does not mean you’re safe from it. Indeed, some studies indicate that a second bout of dengue fever often can be worse than the first, with a greater risk of progressing to the hemorrhagic form.

Do you remember SARS (Severe Acute Respiratory Syndrome)? It popped up in China in 2002 and spread to more than 25 countries before we could blink.

PKIDs landed a group of disease prevention educators in China just as the world became aware of this outbreak that would rapidly become an epidemic. It was coincidence, of course. The trip had been planned for months.

But, our proximity to the SARS outbreak was a reminder to us of how efficient air travel is at spreading germs.

In 2009, there were 2.5 billion airline passengers and that number is expected to increase to 3.3 billion by 2014. That’s a lot of sneezing, coughing, and just plain touching of armrests, overheads, and other surfaces going on in small spaces.

Dr. Alexandra Mangili and Dr. Mark Gendreau wrote a piece for the Lancet in 2005 that talks about the mechanics of disease transmission in an airplane. It’s very good, if you have a few minutes to read it.

They explain air flow patterns and how much air is recirculated (50% and that’s through filters). Turns out, air does not flow the length of the plane, but rather in sections or pockets along the width of the plane. Still an efficient method of disease transmission for airborne and large droplet transmission, but not the only way germs are spread onboard.

According to the article, the most common infections on aircraft have been via the fecal-oral route through contaminated food, although that has diminished in the last few years, possibly due to prepackaged food products and more care in the prepping and handling of food.

Mosquitos, a common vector for diseases such as dengue and malaria, often hitch rides on airplanes. Mangili and Gendreau point out that, “Many cases of malaria occurring in and around airports all over the world in people who had not travelled to endemic areas, known as airport malaria, is evidence that malaria-carrying mosquitoes can be imported on aircraft.”

The cabins of airplanes cannot be thoroughly disinfected between flights. Many times, a plane lands, passengers disembark, and more passengers are seated within 30 minutes. Think of all the droplets of goo left behind that the cleaning crew cannot remove, and the many surfaces that can’t be disinfected.

Keeping one’s hands clean throughout the flight will go a long way toward preventing transmission, and staying up-to-date on your vaccinations for your home country and your destination. As for masks, the authors say, “Although masks play a crucial part in infection control in health care settings, their use is unproven in disease control within the aircraft cabin.” But they do recommend masking and isolating someone suspected of having SARS.

Every year on this planet, malaria kills roughly one million people, many of them children. Scientists are trying to change that number.

Given that malaria is transmitted by the mosquito, which only lives about a month, shortening the mosquito lifespan could reduce the number of infections. At least in theory.

Dr. Michael Riehle and his staff at the University of Arizona have been busy engineering a GM (genetically modified) mosquito. They’ve shortened the lifespan of the mosquito without modifying its essential functions, and this could change the lives of people who live with the threat of malaria on a daily basis.

The bugaboo is that genetically modifying insects, plants, and animals can result in unintended consequences. There are scenarios that can’t be tested in a laboratory environment, or anticipated in the wild. For instance, what if the GM mosquito, unable to transmit malaria due to a shortened life span, is the perfect vector for transmission of some other disease?

In the U.S., numerous exotic species have been introduced accidently—and intentionally. Many have become invasive species. The kudzu vine, the Japanese beetle, the snakehead fish, pythons, and the elm bark beetle are a few in a long list of species that have endangered indigenous plants, fish and animals because they have no natural predators in their new habitat.

Today we have GMOs (genetically modified organisms), including bacteria, plants and animals, that have been highly successful in the lab advancing medical research.

GM plants have been used in the fields and the foods we eat since the early 1990s. Staple crops like corn, soy beans, and tomatoes are some GM crops. Have there been ramifications? Are there health implications? Can we even identify the products that are genetically modified?

Just recently, GM canola plants, which are pesticide-resistant, have been found cross-pollinating in the wild with weeds. The repercussions are not yet known. Meanwhile, genetically engineered sugar beets, responsible for 50 percent of our sugar, have been tabled due to a federal court ruling.

Various GM lab animals and GM crops and livestock are on the docket for FDA review. There is the potential for benefit, but there is also concern.

Currently there is nothing stopping someone from introducing these GM mosquitos, which could be the answer to many prayers, or a possible “frankenfish.”

There are proponents and opponents in the GM debate. On which side do you land?

Mosquitoes are back, and so is West Nile virus (WNV). It was first identified in Africa in 1937, and made its way to New York in the summer of 1999.It’s pretty much all over the country now.

Remember when WNV dominated the news, and we were told not to touch dead birds? Well, as it turns out, WNV transmission is through mosquitoes that bite infected birds, carry the virus in their saliva, and then bite humans or animals.

There are other forms of transmission, including through organ transplants and blood transfusions. Transmission from mother to unborn child and through breast milk is possible, although CDC says the chances are so remote, one should not stop breastfeeding because of risk of WNV infection.

For the most part, WNV is pretty benign, with few or no symptoms. The incubation period is 3 to 14 days. Of those infected, 20% may develop West Nile fever, which can cause flu-like symptoms and lasts less than a week.

It’s possible to become infected through transfusions or transplantation. Donated blood is screened for seven infectious agents, including WNV. The complication that arises is the lack of consistency and standardization in screening blood for WNV, as logistics play a role in the process. Protocols may be more rigorous in areas where WNV is more prevalent. The more sensitive testing is costly and time-consuming.

Then there’s screening of donated organs. Time and test sensitivity are factors. Do the risks of an organ potentially infected with WNV outweigh the benefit of the time necessary to test a donated organ for WNV? Should a standardized protocol be utilized, or should WNV geographic prevalence play a role in determining protocols? And finally, should recipients have a choice in accepting organs that are potentially infected with WNV, without testing?

There are no certain answers to these questions.

Prevention of WNV is what you would suspect: limiting your exposure to mosquitoes by wearing protective clothing or mosquito repellent, and by eliminating breeding areas. Check out this tool and find the perfect repellent that meets your needs! In addition to repellent, make sure you follow these suggestions to minimize your exposure to WNV-carrying mosquitoes:

Disclaimer

The information on PKIDs' Blog is for educational purposes only and should not be considered to be medical advice. It is not meant to replace the advice of the physician who cares for you or your child. All medical advice and information should be considered to be incomplete without a physical exam, which is not possible without a visit to your doctor.